Flotation of ilmenite ores



Patented June 19, 1951 2,557,455 FLOTATION F ILMENITE oars Samuel PayneMeyer, Greenwich, Conn., assignor to American Cyanamid Company, NewYork, N. Y., a corporation of Maine No Drawing. Application March 12,1948, Serial No. 14,638

- 1 Claim. 1

This invention relates to the beneficiation of metallic-oxide mineralsfrom those ores containing excessive amounts of phosphorous-bearinggangue. More particularly, it is concerned with the separation by frothflotation of titanium oxide minerals from low-grade ores containingexcessive amounts of such phosphate-bearing minerals as apatite and thelike.

Titanium oxides have become increasingly important in use, andaccordingly, the demand for high-grade ore from which they may bechemically recovered is steadily increasing. Unfortunately, whilenatural deposits of titaniumbearing minerals are not infrequent, suchores are usually of too low grade for commercial recovery of titaniumoxides directly therefrom. If they are to be effectively utilized, theore must be beneficiated to increase the titaniferous content. Anothersource of titanium oxides are various incidental, or by-product,ilmenite concentrates obtained in working an ore primarily for someother purpose. They too, usually require beneficiation.

The term ore is used herein in its ordinary sense to include both ore asmined and minerals mixtures in such partially beneficiated concentrates.Such ores frequently contain, as a gangue constituent, quantities ofphosphorous-bearing minerals, apatite, for example, being very commonlyfound. The P205 assay may vary from less than 1% in ilmeniteconcentrates which have been obtained from ores worked primarily forother constituents,-to as high as 12 to 15% as found in ores such'asfnelsonite and the like. This is particularly unfortunate since a P205assay in excess of about 0.2% is unacceptable in the production oftitanium oxide pigments. Below 0.13% is desirable, particularly in theanatase crystal form production.

For various reasons, largely procedural and economic, it is desirable touse an anionic-type of promoter for the metal oxide minerals.Unfortunately, many phosphate-bearing minerals, apatite, for example,float readily in the presence of most such promoters. Effectivedepressants for the apatite which do not also depress ilmenite have nothave been known. As a result, most beneficiation procedures used withsuch were unsatisfactory either as to the grade or the recovery or both.

Accordingly, it ishighly desirable to find a beneficiation procedure,involving only a single operation capable of producing an ilmeniteconcentrate of sufficiently low P205 content and in high recovery. Itis, therefore, the principal object of the present invention to producesuch an adaptation and to develop a suitable reagent combinationtherefor. Such a process should enable the use of a single operation ofrougher and cleaner flotations to produce an ilmenite concentrate ofsuch grade as to be capable of utilization in a pigment production.

Surprisingly, the desired objects of the invention are quite simplyaccomplished by the use of novel fluoride or fluosilicate conditioningagents under acidic conditions. The mechanical handling is simple andeffective. An aqueous pulp of the ore is conditioned with a reagentscombination capable of maintaining an acid pH and free fluoride and/orsilicofluoride ions in the circuit. This may be done prior to orconcurrently with conditioningwith the promoter. The ilmeniteconcentrate is then taken directly therefrom. Effective and highlyselective depression of the phosphorous-bearing minerals is obtained.Using this reagent combination in a single operation comprising arougher and one or more cleaner flotations produces eflicient recoveryof the 'IiOz content, accompanied by a reduction in the P205 content toor below the 0.12% level.

It is an advantage of the present invention that it does not require anyexcessive pretreatment of the ore. Usually these ores require quite finesize reduction, usually to below 28 mesh and often to mesh, to unlockthe mineral values from the gangue constituents. Any crushing orgrinding, which is sufllcient to unlock the mineral values, is, ingeneral, adequate for the purposes of the flotation operation.

Since many titanium ores slime freely, a desliming operation is helpful.It is advantageous that rough desliming is ordinarily sufficient, it

being wholly unnecessary to attempt to carry out a quantitativvedesliming. A good general practice is to first rough crush the ore to asuitable degree, for example about -l.0 to 0.5 inch. This material isthen washed, ground to a suitable size, and then finally deslimed.Desliming is usually done by hydraulic classification. Screening may beused but is not as generally practical in use because only the materialbelow about 10-20 microns is ordinarily discarded.

This partially deslimed ore may then be fed directly to the treatment ofthe present invention. However, if so desired, the coarser sizes may beseparated out and treated in any other desired manner as by tabling,jigging, and the like. This again is not necessary. The choice is basedon considerations other than the ability of the present process toconcentrate the ore. Whatever procedure is chosen, that fraction of theore to be treated by froth flotation is made up into a pulp with waterand conditioned with the reagents and floated.

Preferably, the pulp should be conditioned with the reagents at a higherdensity than that normally used in the flotation cells. This highsolidsconditioning aids in insuring thorough dissemination of the reagents, atleast a major portion of which are generally added at this stage. Asolids content of 30-40% is good practice, with even higher solidscontent being used if the necessary apparatus for its handling isavailable. Where conditioning at high solids, or even conlike, as wellas the various commercial mixtures thereof. In addition, certainnaphthenic acids may be used, alone or in combination with the fattyacids. Such naturally-occurring mixtures of fatty and resin acids asfound in talloel are also satisfactory. The promoter is preferably addedas the free acid. If necessary it may be used as a sodium, potassium orammonium neutralized soap thereof but the latter procedure is not to bepreferred. The flotation circuit will be acidic and the presence ofalkali soap-forming ions makes control less certain. Sulfates and/ orsulfonates such as found in certain of the sulfonated petroleumhydrocarbon reagents should not be used since the depression of apatiteas done in this invention is not effective in their presence. 7

The amount of promoter used will vary with the nature of the ore, thewater conditions, i. e., temperature, acidity, hardness, etc. of thewater and the average particle size mineral and content of the feedbeing treated. In general, amounts ranging from 0.5 to 10 lbs.+ton ofore treated, with an average of about 1.5 to 3.0 lbs/ton constitutingthe average practice will be necessary. In some cases a frother may behelpful. Where a frother is desirable or necessary, any suitable typesuch as pine oil, cresylic acids, and the commercial higher-alcoholfrothers may be used. Frothers of the sulfated alcohol type should notbe used as they tend to adversely effect the depression of apatite.

Of primary importance is the use of the novel depressant of the presentinvention. As noted above, this depressant should be an eflective sourceof fluoride and/or fluosilicate ions. The particular source may bevaried. The necessary ions may be provided, for example, by addingfluosilicic acid, per se or as a soluble salt thereof. Where the circuititself is not normally acidic it should be made so. This may be done byadding an acid such as HF or HaSiFs. It may also be done by adding asoluble fluosilicate, such as that of sodium or potassium, since thesesalts have an acid reaction. Similarly a combination of a mineral acid,sulfuric, hydrochloric or the like may be used with a soluble fluorideor acid fluoride such as those of sodium, potassium or ammonium.Although certain sulfate containing reagents should not be used, asnoted above, sulfuric acid does not afiect the apatite depression. whenused with a soluble fluoride as a source of fluoride ions the procedureis wholly successful.

As to the amount of depressant used, the demand may be quite flexible.depending upon the nature of the ore, the temperature, acidity, hardnessetc., of the process water and the particular agent used. Smalleramounts of phosphate mineral, obviously require smaller amounts ofdepressant. In general, the amount used will vary from about 0.1 toabout 4.0 lbs/ton of feed. A good general practice is to add about 1.5to 2.0 lbs/ton in the initial conditioning operation, or to the cellsduring the rougher flotation if preconditioning is not used. A part maybe withheld and added during cleaning or an additional amount or amountsmay be so added if desired.

Actually, numerical weight limitations are not as helpful as aconsideration of the pH during flotation. As noted, deflnitelyacidicconditions, a pH less than 6.8, are necessary. A pH below 6.0 is better.Dropping below about 4.5 does appear to help although a lower pH may bereached as-a result of other conditions and does no harm. Solublefluosilicates make excellent reagents for this reason. They are not onlyacid in reaction but appear to be somewhat self -bufi ering, producing apH of about 4.5-5.5 as long as there is a suflicient amount present. Inusing the fluosilicates one precaution should be taken. If the processwater is very cold it is helpful to warm it slightly since thesolubility of the salt increases rapidly above about 20 C.

The lower pH values may be produced directly in the conditioning step orin the cell during the rougher flotation. When this is done, any rise inpH through dilution in the cleaner step or steps may be ignored. Thisprocedure being the simplest is perhaps preferable. On the other hand,it may be desirable to conduct the rougher float at a higher pH, i. e.,5.5-6.8, and drop down to the lower pH during cleaning by subsequentacid addition. Either procedure is effective in obtaining the desiredresult.

This invention will be further illustrated in conjunction with thefollowing examples which are intended as illustrative only. All partsare by weight unless otherwise noted.

EXAMPLE 1 A sample of primary Nelsonite ore, comprising ilmenite with anapatite gangue was given a preliminary treatment by rough crushing tominus washing, grinding to minus 65 mesh, and rough desliming. A pulp ofthe partially deslimed ore comprising about 30% solids in water wasconditioned for ten minutes with 2.5 lbs/ton of talloel and 2.0 lbs/tonof sodium silicofluoride (NaaSiFc) at a pulp temperature of about 30 C;This conditioned pulp was then reduced to about 20% solids, the ilmeniteconcentrate floated, and

'the concentrate was cleaned and recleaned, and

the cleaner tailings were combined for analysis. Average results areshown in the following table.

Table I Assay Distribution Product Per Per Per Cent Cent Cent TlO;

wt. Tioz no.

Head (deslimed) 100. 0 22. 47 7. Ilmenite Concentrate... I 40.8 42. 400. Cleaner Tailings (combined .1 30.06 1. 1 4.85 15.

9 Rougher Tailing 50.

Conditioned pulp before dilution, pH-M).

EXAMPLE 2 tails were combined. Typical results are shown in thefollowing Table II.

An apatite-ilmenite concentrate produced by gravity concentration andanalyzing 38% TiOz and 6% P205 was ground to pass a 65 mesh screen,deslimed and made up into a pulp at about 6 5% solids. This pulp wasconditioned for 10 minutes with 1 lb./ton of sulfuric acid, 2 lbs/ton ofsodium fluoride, 1.5 lbs/ton of oleic acid and 0.1 lb./ton of analcoholic frother. The conditioned pulp was diluted to 22% solids and anilmenite concentrate floated for 5 minutes. This concentrate 6 ess ofthe present invention is very effective in producing very low P205 assayconcentrates. However, the procedure of the present invention may beused as a pretreatment for certain other apatite-ilmenite separatingprocesses. One such process is that disclosed in the application for U.S. Letters Patent of McMurray and Moyer, Serial No. 636,228, filedDecember 20, 1945, now Patent Number 2,525,146 in which caustic starchis used to depress ilmenite, and apatite is floated therefrom with ananionic promoter such as 'a soap of talloel or a fatty acid.

This latterprocedure is particularly effective as an after treatment inconjunction with the present process. In the instant application isshown a process which makes a good concentration of ilmenite with highrecovery in a product containing only a small amount of the phosphate.

Instead of repeating the operation, that is, again floating ilmenitefrom apatite, to reduce the P205 assay, a pulp of this concentrate maybe neutralized and then treated in accordance with the above mentionedprocedure of McMurray and Moyer. In this way a major portion of theresidual small amount of phosphate-bearing minerals may be readilyfloated away from the titaniumbearing minerals. In some instances thiscomwas given a single 4 minute cleaning. The

cleaned concentrate constituted 70% by weight of the feed, contained 82%of the ilmenite and assayed T102. 96.5% of the P205 content was removedin the rougher tail and an additional 1.4% in the cleaner tail.

In the foregoing examples it has been shown that the procedure of thepresent invention is wholly effective in reducing the P205 assay. Forsome purposes, particularly for the manufacture of the anatase crystalform it may be desirable further to reduce the P205 content. This can bedone in any of several ways.

One efiective procedure is to repeat the treatment of the presentinvention on a cleaned concentrate previously obtained. This operationagain is simple. The pulp of the ore is conditioned with additionalamounts of the depressant reagent and promoter. This conditioned pulp isfloated and the concentrate cleaned in the usual manner: An illustrationof this procedure is shown in the following example.

EXAMPLE 4 The ilmenite concentrate obtained in Example 1 was repulpedwith water to about 30% solids and conditioned for 5 minutes with 1lb./ton of NaZSiFGJ The conditioned pulp was diluted to about 20% solidsand the ilmenite concentrate flotation made using 1.0 lb./ton of talloelas the In the preceding example the procedure isin efiect a multiplestage operation in which the apatite depressant reagents of the presentinvention are added in each stage. So used, the procbined operation hasthe advantages that overall reagent consumption may be reduced, and thepretreatment need not be so carefully controlled to reject P205 contentand the final ilmenite concentrate is of extremely high grade. Thisprocedure is shown in the following example.

EXAMPLE 5 A'sample of nelsonite ore was prepared in accordance with theprocedure shown, in Example 1. After desliming, a pulp of the ore atabout 50% solids, was conditioned for 5 minutes with 2 lbs/ton of sodiumsilicofluoride and then an additional 5 minutes with3 lbs/ton oftalloel. The conditioned pulp was diluted to 20% solids and a rougherilmenite concentrate taken for 4 minutes. This concentrate was given acleaner and recleaner flotation of 3 minutes each without additionalreagents. This procedure proapatite concentrate taken for 3 minutesusing 0.5 lbs/ton of sodium saponified talloel. An extremely low P205content ilmenite concentrate was produced as machine discharge. Detailedresults of this test are shown in the following Table IV.

Table IV Assay Distribution Product Per Per Per Per -Per Cent Cent CentCent Cent Weight TlOz P205 TiO; P30;

Head (deslimed) 100. 0 17. 40 7. 36 100. 0 100. 0 Rgh. Apatite Ct 6. 229. 10. 18 10. 6 8. 6 Final Ilmcnitc Ct. or

Machine Dischargc 28. 3. 43.20 0.05 70.3 0. 2 Calc. Reclcancd llmc- Inite Ct 34. 5 40.81 0.19 80. 9 8.8 Recleaner Tailing 3. 6 30. 98 1. 776. 4 0. 9 Cleaner 'Iailing- 5. 3 18. 42 2. 02 5. 6 1. 5 Rougher Telling-56. 6 2. 18 11.56 v 7.1 88. 8

- spends I claim A process of beneiiciating mineral mixtures comprisingat least ilmenite and an excessive amount of apatite as gangue, saidmixture beins in particle sizes suitable for froth flotation-feed. whichcomprises the steps of forming an aqueous pulp of the mixture,subjecting said aqueous pulp to froth flotation at a pH less than 8.8 inthe presence of an anionic promoter selected from the group consistingof the sulfate and sulfonatefree higher fatty acids, resin acids,naphthenic acids, talloel, mixtures thereof, and the sodium. potassium,and ammonium soaps of these materials and a selective depressant for theapatite containing a source of free ions selected from the groupconsisting of fluoride and fluosilicate ions, and collecting theresultant ilmenite bearing froth concentrate, whereby a concentrate ofin-. creased T10: and decreased P205 assay is obtained.

' T SAMUEL PAYNE MOYER.

summons orrm The following references are of record in the me of thispatent:

UNITED STATES PATENTS OTHER REFERENCES Gutzeit Archives des SciencePhysical 8: Naturales, vol. 21, pp. 260, 269, 1939.

Bureau of Mines, Report of Investigation 3397, pp.36, 37.

